Grinding machine with supplemental motion

ABSTRACT

A grinding tool is formed of a grinding shoe ( 1 ) and an actuator ( 2 ) that acts upon the grinding shoe ( 1 ) and is characterized by a horizontal displacement (H) acting essentially parallel to the surface ( 8 ) of a material ( 9 ) to be worked and a perpendicular to the surface ( 8 ). The grinding shoe ( 1 ) is resiliently mounted by a spring element ( 3 ) in a housing ( 4 ) enclosing the actuator ( 2 ). Two spaced cylindrical grinding rollers ( 5 ) provide guidance of a grinding means ( 6 ), such as a grinding or abrasive belt. By superimposing the displacement (H) with a perpendicular displacement (V) the efficiency of the grinding process is generally increased.

FIELD OF THE INVENTION

[0001] The invention relates to a grinding tool having a grinding means detachably fastened to a grinding shoe for working the surface of a workpiece, wherein the grinding shoe can be imparted a movement by an actuator, the movement being initially a displacement motion running parallel to the surface of the workpiece.

BACKGROUND OF THE INVENTION

[0002] Grinding tools of the type described above are used in working a surface of a workpiece. Movement is imparted to the grinding shoe with the grinding means by an actuator, for example an electrical motor. The grinding means, for example an abrasive or grinding paper or an abrasive or grinding belt, is arranged on the side of the grinding shoe facing the surface to be worked. In so far as the grinding means, to which the grinding shoe imparts movement, is in movement, it carries away particles from the surface. Depending on the application and the basic conditions, the grinding tool can be designed as free-standing or as a handtool device.

[0003] DE 3 644 499 discloses a manually operated grinding tool having a grinding shoe that can be moved parallel to a surface to be worked and having a grinding means. The movement is produced by an electrical motor.

[0004] The disadvantage of this known solution is that only minimal abrasive removal performance is effected. For the user, for example, this results in high time and energy expenditure, the latter being the result of the high contact pressure forces required.

SUMMARY OF THE INVENTION

[0005] The object of the present invention is to create a grinding tool with high abrasive removal capacity. Further, the grinding tool can be economically manufactured and used without great energy expenditure.

[0006] The object is achieved, according to the invention, in that the movement exhibits a displacement movement, that is effected perpendicularly to the surface being worked.

[0007] The abrasive removal performance is increased to a considerable degree in that the perpendicular displacement exhibits a component acting perpendicular to the surface of the workpiece. In particular, this results in an extremely efficient grinding process. Moreover, such displacement contributes to shaking the particles removed from the surface out of the grinding means, in particular from the abrasive or grinding paper, which contributes to a longer service life of the grinding means.

[0008] Preferably, the perpendicular displacement runs a sinusoidal course as a factor of time, in order to obtain the most uniform movement possible perpendicular to the surface being worked. When this occurs there is only minimum stressing, due to the vibration caused by the perpendicular displacement, for the user of the grinding tool.

[0009] Advantageously, the perpendicular displacement is a time-dependent pulsating displacement in order to achieve an optimum level of effect.

[0010] The perpendicular displacement preferably is of a frequency of 1 Hz to 500 Hz in order to permit the highest possible efficiency of the grinding process.

[0011] In a preferred embodiment the perpendicular displacement exhibits an amplitude in the range of 10 μm to 500 μm. The efficiency of the grinding process is optimal in the range of these amplitudes.

[0012] The perpendicular displacement advantageously acts on the entire face of the grinding shoe in contact with the work surface and so permits uniform abrasive removal over the entire grinding shoe. In particular, this results in a uniform loading of the grinding means, which in turn has a positive affect on the length of the service life of the grinding means, in particular that of grinding or abrasive paper.

[0013] In a further embodiment for special conditions, the perpendicular displacement acts punctiform on the side of the grinding shoe in contact with the work surface.

[0014] The actuator for the grinding shoe advantageously has a piezo element for producing the perpendicular displacement. The advantage of the piezo element is its extremely compact construction and the simple control of the actuator.

[0015] Preferably, the actuator has a motor-driven eccentric shaft for producing the perpendicular displacement, since the shaft assures economical manufacture of the grinding tool. An electrical motor, for example, is provided as the drive for the eccentric shaft.

[0016] Advantageously, the actuator includes a linear motor to provide an easily controllable actuator and an economical drive for the grinding shoe.

[0017] Preferably, the actuator can be controlled by an electronic control unit which takes into consideration an input signal from a sensor arranged in the grinding unit. The sensor evaluates, for example, the reflectance waves from the workpiece and determines on that basis the material of the workpiece. The information so obtained is, for example, taken into consideration in the control unit for controlling, for example, the amplitude and frequency for the displacement. The control unit can, for example, be designed as a microprocessor or also as an analog circuit.

BRIEF DESCRIPTION OF THE INVENTION

[0018] In the following, the invention is more completely explained along with an exemplary embodiment, wherein:

[0019]FIG. 1 is a side view of a grinding tool in partial section;

[0020]FIG. 2 represents a sinusoidal course of the perpendicular displacement as a factor of time;

[0021]FIG. 3 represents a saw-tooth course of the perpendicular displacement as a factor of time; and

[0022]FIG. 4 represents a rectangular course of the perpendicular displacement as a factor of time.

DETAILED DESCRIPTION OF THE INVENTION

[0023]FIG. 1 represents a grinding tool according to the invention comprised of a grinding shoe 1 and an actuator 2 acting on the grinding shoe 1. The grinding shoe 1 is resiliently mounted by means of a fastening element 3 to a housing 4 that encloses the actuator 2. Two spaced cylindrical grinding rollers 5 provide guidance of a grinding means 6, in particular a grinding or abrasive belt. The grinding rollers 5 are driven in the direction D by an electrical motor (not shown for space reasons). The grinding tool with its grinding means lies upon a surface 8 of a work piece 9.

[0024] The actuator 2 acts perpendicularly to the surface 8 of the workpiece 9 by means of a perpendicular displacement V as viewed in FIG. 1. The grinding means 6 located between the grinding shoe 1 and the surface 8, is superimposed additionally by the horizontal displacement H resulting from the rotation D of the grinding rollers 6. The external surface 11 of the grinder rollers 5 can, for example, have a coating of rubber in order to increase the friction between the external surface 11 and the grinding means 6 and consequently prevent slippage of the grinding means 6 on the grinding rollers 5. It should be appreciated that surface 8 could be vertical rather than horizontal or at an angle between vertical and horizontal.

[0025] The housing 4 includes a handle 12 at one end for guiding the grinding tool, the handle being equipped with an actuation switch 13 for on- off-control of the electrical motor and the actuator 2. Further, the housing has on the end opposite the handle 12, a guidance knob 14, in order to be able to apply a greater pressure force on the grinding tool.

[0026] A control unit 16 is situated inside the housing 4; the control unit provides for the control of the actuator and the electrical motor. A sensor 17 arranged in the grinding shoe generates an input signal 18 for the control unit 16. The sensor 17 evaluates, for example, the reflectance waves produced by the workpiece and deduces therefrom the nature of the material of the workpiece 9. The information I obtained in this fashion is taken into consideration, for example in the control unit 16, for control of the amplitude A and the frequency f for the displacement. The control unit 16 can, for example, be designed as a microprocessor or even as an analog circuit.

[0027] Different courses of the amplitude A of the perpendicular displacement as a factor of time t are represented in FIGS. 2 to 4. 

What is claimed is:
 1. A grinding tool comprises a grinding means (6), a grinding shoe (1) acting on said grinding means for working a surface (8) of a workpiece (9), an actuator (2), acting on said grinding shoe (1), said grinding shoe (1) being arranged to effect a movement via said actuator (2) wherein the movement includes a first movement (H) extending parallel to the surface (8) of the workpiece and a second movement (V) extending perpendicular to the surface (8) of the workpiece.
 2. A grinding tool, as set forth in claim 1, wherein said second movement (V) runs a generally sinusoidal course as a factor of time (t).
 3. A grinding tool, as set forth in claim 1, wherein said second movement (V) runs a pulsating course as a factor of time (t).
 4. A grinding tool, as set forth in claim 1, wherein said second movement (V) has a frequency in the range of 1 Hz to 500 Hz.
 5. A grinding tool, as set forth in claim 1, wherein said second movement (V) has an amplitude (A) in the range of 10 μm to 500 μm.
 6. A grinding tool, as set forth in claim 1, wherein said second movement (V) acts over the entire surface of said grinding means (6) in contact with the surface (8) of the workpiece (9).
 7. A grinding tool, as set forth in claim 1, wherein said second movement (V) acts punctiform on said surface of said grinding means in contact with the surface (8) of the workpiece (9).
 8. A grinding tool, as set forth in claim 1, wherein said actuator (2) comprises a piezo element for producing said second movement (V).
 9. A grinding tool, as set forth in claim 1, wherein said actuator (2) comprises a motor-driven eccentric shaft for producing said second movement (V).
 10. A grinding tool, as set forth in claim 1, wherein said actuator (2) is controlled by an electronic control unit (16) based on an input signal from a sensor (17) located in said grinding shoe (1). 